1. Field of the Invention
The present invention relates to enhancing the dissolution of certain heteropolysaccharides in aqueous media and, more especially, to increasing the viscosity over time of such heteropolysaccharide solutions by effecting the dissolution of the said heteropolysaccharide conjointly with at least one organic acid or anhydride thereof having at least one pK of a value between 5 and 7. The invention also relates to a novel composition of matter comprising the said heteropolysaccharide and the said organic acid or anhydride thereof.
2. Description of the Prior Art
In an effort to increase the viscosities of a variety of aqueous media over a wide pH range and a wide range of salt contents, it is not uncommon in the prior art to utilize as the viscosity increasing ingredient those heteropolysaccharides obtained through fermentation of carbohydrates by means of bacteria of the genus Xanthomonas.
According to one of the known methods for the preparation of such heteropolysaccharides, the biopolymer is precipitated from the reaction mixture in the form of a complex calcium salt. This precipitation is effected, for example, by precipitating calcium hydroxide, in situ, via addition of sodium hydroxide solution and calcium chloride to the must resulting from the fermentation. Another method of precipitation includes charging the fermented must into milk of lime. Compare U.S. Pat. No. 3,232,929. In each instance, the precipitate is collected according to conventional techniques, such as filtration, and is then dried, e.g., in a ventilated oven, and ground. The biopolymer is thus converted to powder form.
Nevertheless, the subsequent use of such calcium salt of the biopolymer presents a vexing problem by reason of the poor water solubility thereof.